Hertel exophthalmometry versus computed tomography and optical

lnt. J. Oral Max illofac. Surg. 2004; 33: 125-!33
doi: 10.1 054/ijom.2002.0481, available online at http://www.sciencedirect.com
lnt.emationol Journal
?f
Oral&_
Max1llcjacial
Surgery
Leading Clinical Paper
Trauma
Hertel exophthalmometry
versus computed tomography
and optical 3D imaging for the
determination of the globe
position in zygomatic fractures
E. Nkenke1 , T. Maier2 , M. Benz2 ,
J. Wiltfang\ L. M. Holbach 3 ,
M. Kramer 1 , G. Häusler2,
F. W. Neukam 1
1
Department of Oral and Maxillofacial Surgery,
University of Erlangen-Nuremberg, Glueckstr.
11, 91054 Erlangen, Germany; 2 University of
Erlangen-Nuremberg, Staudtstr. 7, 91058
Erlangen, Germany; 3 Department of
Ophthalmology, University of
Erlangen-Nuremberg, Schwabachanlage 6,
91054 Erlangen, Germany
E. Nkenke, T Maier, M. Benz, J Wiltfang, L. M. Ho/bach, M. Kramer,
G. Häusler, F. W Neukam: Hertel exophthalmometry versus computed tomography
and optical 3D imaging for the determination of the globe position in zygomatic
fractures. Int. J. Oral Maxillofac. Surg. 2004; 33: 125- 133. © 2003 International
Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All
rights reserved.
Abstract. It has been the aim of the present study, to introduce the combination of
computed tomography and optical 3D imaging to exophthalmometry and to
compare the resulting data to the dassie Hertel method. Twenty patients without
orbital pathology and 12 patients were included in the study, who were subjected
to apreoperative computed tomography. Optical 3D images of the facial surface
were assessed and Hertel exophthalmometry was carried out to determine
protrusion. In patients with zygomatic fractures the assessment of optical 3D
images and Hertel values was repeated 5 days after surgery. Preoperative axial CT
slices and postoperative optical contours through the globes were superimposed
and the change in protrusion was determined. The protrusion values assessed either
by CT, Hertel exophthalmometry or optical 3D imaging for patients without
orbital pathology did not show any statistically significant differences between each
other. F or zygomatic fractures, Hertel exophthalmometry revealed more
pronounced protrusion data in four of five cases of a posterolaterally dislocated
lateral orbital rim and a higher degree of enophthalmos in cases without
dislocation of the lateral orbital rim than it could be proved in the CT slices. The
differences between optical measurements and CT data were minimal in patients
with zygomatic fractures . The combination of computed tomography as baseline
measurement and optical 3D imaging for the follow-up examinations reveal more
realistic data in cases of zygomatic fractures than Hertel measurements and should
be preferred.
The problern of accurate measurement
of exophthalmos and enophthalmos has
eluded scientists for over 100 years. The
degree of the changes of globe position is
090 1-502 7/04/020 125 + 09 $30.00/0
©
an important clinical sign in different
orbital diseases including traumatology.
There are three categories of exophthalmos. The first is absolute, which refers to
Key words: computed tomography;
exophthalmos; Hertel exophthalmometer;
optical 30 imaging; zygomatic fractures.
Accepted for publication 29 July 2003
an eye that protrudes beyond the range
of normal on a single determination. The
second is relative exophthalmos, which
relates to the fellow eye, and the third
2003 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
126
Nkenke e t al.
Table 1. Basic patient data
N
No pathology
Zygomatic fracture
Fernale
Male
20
8
12
12
I (left side)
7 (left side)
5 (right side)
is comparative exophthalmos, which
denotes a change in eye position over a
time interval 2 •
Although several methods have been
proposed to evaluate the globe position,
the Hertel exophthalmometer is most
frequently used as a simple tool in the
evaluation of proptosis. It has been
objected on its use that it shows a low
reliability and a poor repeatability in
serial measurements 16 . The difficulties
with this method are weil known.
They include asymmetry of the lateral
orbital rims, compression of soft tissues,
parallax errors and Iack of uniform
technique 5 •
Orbit computerized tomography helps
to achieve more accurate values in
exophthalmometry 13 . A major drawback is the exposure of the patient
to irradiation. Stereophotogrammetric
exophthalmometry has been used in
experimental set-ups, but has never been
applied in clinical routine 1 •
The use of optical 3D imaging has
been recently introduced to medical
sciences with high accuracy. It is used to
assess optical 3D surface data in vivo in
a non-contact, non-invasive wai 8 . It
seemed reasonable to extend its use to
exophthalmometry.
It has been the aim of the present
study to determine the globe position in
20 adults without pathology of the
orbital complex and in 12 patients suffering from zygomatic fractures by
Hertel exophthalmometry, computed
tomography and optical 3D imaging
in order to compare the results of the
different methods.
Patients and methods
The study was based on 20 patients (8
female, 12 male, 49.1 ± 17.3 years), who
were examined by computed tomography of head and neck for the exclusion
of different diseases. Patients were
selected, when they did not show any
accompanying pathology of the midface.
Another 12 patients (1 female, 11 male,
38.6 ± 18.3 years), who received routine
orbital computed tomography because
of zygomatic fractures, were included
in the study (Table 1). The study
was approved by the Institutional
Mean age
(years)
49.1
38.6
± 17.3
± 18.3
Ethics Committee of the University
of Erlangen-Nuremberg (number of
approval 2221). All patients gave their
informed consent to the participation in
the study. Exclusion criteria were refractive errors, ocular hypotony, deviation
of the nasal septum, nasal bone
fractures, bilateral orbital fractures,
and associated intraocular trauma. In
patients with zygomatic fractures , the
superficial sensory function of the
infraorbital nerve was assessed by
the Pointed Blunt Test, bilaterally.
Moreover, these patients were examined
by ophtha1mologists, preoperative1y and
on the 5th day after surgery. Clinically
detectable disorders of ocular motility
and diplopia were documented. The different exophthalmometry measurements
were carried out at the day of injury and
5 days postoperatively (Fig. 1).
As standard technique for the assessment of the globe position, Hertel
exophthalmometry was used. With a
binocular device (Exophthalmometer
nach Hertel, Oculus Optikgeräte,
Wetzlar, Germany) the distance from
the corneal apex to a plane defined by
the deepest point on the lateral orbital
rim, on which the footplates of the
device were placed, perpendicular to the
frontal plane, was determined . As base
value, the distance between the two footplates was documented at the first
measurement and reproduced at the
follow-up examinations. By this method,
the apex of the cornea is viewed from
sides using mirrors with superimposed
millimetre rules to assess the degree of
exophthalmos.
CT scans were o btained on a
Somatom Volume Zoom scanner
Optical 30 images of the facial surface
Hertel exophthalmometry
Computed tomography
General ophthalm ological examination
(Siemens, Erlangen, Germany) using
contiguous 1 mm thick axial slices
with gantry tilt of 0° parallel to the
Frankfurt horizontal plane. The data
were transferred to the Osiris medical
imaging software Version 3.1 (Hopitaux
Universitaires de Geneve, Division
d'Informatique
Medicale,
Unite
d'Imagerie
Numerique,
Geneva,
Switzerland). Axial orbital images were
selected that revealed the centre of the
lens, the largest eyeball contour through
the corneal apex and the deepest point of
the lateral orbital rim perpendicular
to the frontal plane with the patients
looking straight forward. Parameters
of absolute exophthalmometry were
assessed according to KIM & CHOI 13 .
They included the distance between the
most anterior points of the lateral orbital
rims of both eyes (A), the shortest distance from the corneal centre to line A
(BcT), the BcTIA ratio, the distance
between the most anterior points of the
lateral orbital rim and the medial orbital
rim (C), the length of the line passing
through the lens centre from the apex to
line C (D), the D/C ratio and the distance between the corneal apex and the
posterior pole (E), which is parallel to
line BcT and perpendicular to A (Fig. 2).
For cases with zygomatic fractures, the
distance A was estimated by generating
a mirror image of the sound side with
nasal septum as axis of symmetry
(Fig. 3).
For the data acquisition of the facial
surface an optical 3D sensor (CAM 30 ,
3D-shape, Erlangen, Germany, http://
www.3D-shape.com/) was used (Fig. 4).
The sensor is based on a modification of
the phase measuring triangulation
method. A sequence of phase-shifted
fring~ patterns of structured light is
projected on the region of interest. From
different directions two CCD cameras
record the data. The images of the
phase-shifted patterns are evaluated by
means of a four-shift-algorithm to
receive the three dimensional shape of
Optical 30 images of the facial surface
Hertel exophthalmometry
General ophthalmologlcal examination
Oays
Maximum Interval
of7 days
4
Oay of lnjury
Oay of surgery
Fig. 1. Flow chart of the study of patients with zygomatic fractures .
Exophthalmometry using 3D imaging
Fig. 2. Axial computed tomography slice of a patient without pathology of the orbital region
representing the exophthalmometry parameters (A=the distance between the most anterior
points of the bony lateral orbital margins; Bcr and Boptic• respectively=the shortest distance
from the corneal centre to line A; C=the distance between lateral and medial orbital margin;
O=the length of the line passing through the centre of the Jens from the corneal centre to line
C; E=anterior-posterior diameter of the globe; F = corresponding contour of the facial surface
assessed by optical 30 imaging).
the object's surface. The 3D sensor takes
advantage of an astigmatic optical
device for the projection of precise sinusoidal intensity coded fringe patterns
instead of a commonly used Renehigrating fringe projection 10 .
The optical 3D sensor was calibrated
for
a measurement volume of
Fig. 3. Axial computed tomography slice of a patient with a left side zygomatic fracture
(Aestimated=estimated distance between the most anterior points of the bony lateral orbital
margin by generating a mirror image of the sound side with the nasal septum as plane of
symmetry; BcT rererence = the shortest distance from the corneal centre assessed by optical 30
imaging to line Aeslimated of the sound side; BcT preop=the shortest distance from the corneal
centre assessed by optical 30 imaging to line Acslimated of the affected side, preoperatively;
Boplic postop = the shortest distance from the corneal cen tre assessed by optical 30 imaging to line
Aestimated of the atTected side, postoperatively; C = axis of symmetry; O=corresponding preoperative contour of the facial surface assessed by optical 30 imaging; E = corresponding
contour of the facial surface 5 days after surgery assessed by optical 30 imaging).
127
300 x 300 x 300 mm 3 , adapted to the
average dimensions of a human head .
The required measurement time for data
acquisition was 640 ms. Matted, grey,
opaque soft contact lenses (Contact
Color prosthetic, Contact Color, Rome,
Italy, base curve 8.80, diopter 0.00,
diameter 14.50 mm) were applied to the
patients, because measurements of the
cornea had turned out to be difficult
because of its glossy surface that produces reflections of the light source of
the optical sensor with the consequence
of measurement breakdown (Fig. 5).
Before the contact lenses were applied to
another patient, disinfection was carried
out with a solution containing 4.5%
glutaraldehyde, 7.4% formaldehyde and
6.4% quaternary ammonium compounds (Mucadont IS, Merz+Co,
Frankfurt, Germany) for 30 min. This
solution is active against HI viruses,
hepatitis viruses, herpes viruses and
adeno viruses. Subsequently, the contact
lenses were stored in another disinfection
solution (Opti-Free, Alcon Laboratories,
Fort Worth, USA) for at least 6 h to
inhibit bacterial growth. Before use, they
were rinsed with saline solution (Eye
See, Lapis Lazuli, Laren, Netherlands).
The cornea was anaesthetized with a
local anaesthetic (Conjuncain EDO, Dr
Mann Pharma, Berlin, Germany) to prevent unpleasant sensations during the
application of the lenses. With the eyes
looking straight forward, the optical 3D
images were acquired.
From the optical 3D images the contour ofthe globes was assessed in a plane
through the corneal apex and the deepest
point of the lateral orbital rim perpendicular to the frontal plane and transferred to the Osiris medical imaging
software (Fig. 6). After superimposition
with corresponding computed tomography slices as parameters of exophthalmometry the shortest distance from the
corneal centre found in the contour of
the optical 3D image to line A (Boptic)
was determined (Fig. 2).
Operations on the patients with zygomatic fractures were carried out within
the first week after injury. General
anaesthesia with oral intubation was
applied. After an incision of 15 mm at
the lateral eyebrow, the fracture at the
frontozygomatic suture was exposed.
The zygomawas reduced percutaneously
by traction with a Strohmayer hook.
The inferior orbital rim and the orbital
floor were explored via a subciliary
approach. After repositioning of the
orbital content, the fragments of the
orbital floor were reduced. If more than
128
Nkenke et al.
Fig. 4. 3D sensor based on phase measuring triangulation (a: CCD camera, b: fringe pattern
projector).
0.5 cm 2 of the orbital floor were missing,
it was reconstructed with an individually
contoured, perforated sheet of polydioxanone (PDS ZX7, Ethicon, Norderstedt,
Germany). By an intraoral approach,
the crista zygomaticoalveolaris was exposed and reduced. For internal fixation, miniplates and monocortical
screws (Champy miniplate osteosynthesis system, Martin Medizintechnik,
Tuttlingen, Germany) were used at the
frontozygomatic suture, the inferior
orbital rim and the crista zygomaticoalveolaris.
Optical 3D imaging and Hertel exophthalmometry were repeated in the
patients with orbital fractures 5 days
after surgery. For the superimposition of
the follow-up examinations, the healthy
orbit was used as reference side and
the protrusion of the reduced side
(Boptic postop) was documented (Fig. 3).
Statistics
Mean values were given with standard
deviations. For comparison of continuous variables in paired samples, the
Wilcoxon Test was used . P-values equal
to or smaller than 0.05 were considered
significant. All calculations were made
using SPSS Version 10 for Windows
(SPSS Inc., Chicago, USA).
Results
In the group of adults without orbital
pathology, the absolute exophthalmometry analysis by computed tomography
revealed a mean value for the distance
between the two bony lateral orbital
rims (A) of 96.6 ± 7.5 mm. The shortest
distance between the corneal apex and
line A (protrusion, BcT) measured
16.7 ± 4.5 mm on the right side and
16.7 ± 4.4 mm on the left side. The difference was not statistically significant
(P = 0.655). The distance between lateral
and medial orbital rim (C) showed a
mean value of 35.9 ± 3.5 mm (right) and
36.0 ± 3.4 mm (left) without statistically
significant difference between the two
sides (P = 0.180) . The length of the line
passing through the lens centre from the
corneal apex to line C (D) revealed a
mean value of 12.2 ± 3.9 mm (right) and
12.4 ± 4.0 mm (left) (P = 0.305). The
anterior-posterior diameter of the globe
(E) was 24.2 ± 2.0 mm on both the left
and the right side (P= 1.0). The BcT/A
ratio and the D/C ratio showed mean
values of 0.17 ± 0.04 and 0.34 ± 0.09 for
both sides, respectively (P=0.655 and
P = 0.374, respectively). BcT-E/2 revealed
a mean va'tue of 4.6 ± 4.0 mm for the
right side and 4.6 ± 3.9 mm for the left
side (P=0.892) (Table 2).
Protrusion assessed by Hertel exophthalmometry showed mean values of
16.2 ± 4.8 mm for the right side and
16.6 ± 3.7 mm for the left side
(P = 0.525). When it was determined by
optical 3D imaging and superimposition
with the CT data, the corresponding
values were 16.6 ± 4.4 mm for both
sides (P = 0.689). The protrusion values
assessed either by Hertel exophthalmometry or by optical 3D imaging did
not show any statistically significant
differences between each other and to
the data extracted from the computed
tomographies (P optic/Hertel right = 0.906,
p optic/Hertel left = 0 ·925,
p CT/Hertel right =
0.722, p CT/Hertel left=0.981, p CT/optic right
= 0.572, P CT/optic left = 0.076).
Hertel-E/2 was 4.5 ± 3.6 mm (right)
and 4.1 ± 4.6 (left), respectively (P =
0.525) . BcT-E/2 and Hertel-E/2, BopticE/2 and Hertel-E/2, and BcT-E/2 and
Boptic-E/2 did not differ significantly
for both sides (P CT/Hertel right = 0. 705,
p CT/Hertelleft = 0.981 ,
p optic/Hertel right =
0.906, poptic/Hertelleft = 0.925, PcT/opticright
= 0.592, PcT/opticleft = 0.114).
Seven zygomatic fractures affecting
the left side and five affecting the right
side were followed up. In eight cases the
Peinted Blunt Test could detect a sensitivity impairment of the innervation area
of the infraorbital nerve on the fractured
side. When holding the head parallel to
the Frankfurt horizontal plane, four
patients suffered from diplopia looking
upward more than lY.
The computed tomographies revealed
an involvement of the orbital floor in the
fracture site and a haematosinus in all
cases. Six fractures of the orbital floor
showed an entrapment of the inferior
Ex ophthalmometry using 3D imaging
Figo 50 Patient with Ieft side zygomatic fracture wearing contact lenses, while a fringe pattern is
projected on him during acquisition of optical datao
rectus muscle. In five patients a dislocation of the lateral orbital rim
of more than 2 mm in dorsolateral
direction was apparent. During the
operations, after the reposition of the
orbital content a repair of the orbital
floor had tobe carried out six times with
a sheet of polydioxanone (PDS ZX7,
Ethicon,
Norderstedt,
Germany),
because the remaining defect was !arger
than 005 cm 2 o
Five days after surgery, diplopia could
no Ionger be found in any of the
patientso The eight cases of sensitivity
disorders remainedo However, all
patients stated that the hypoesthesia
was less pronounced compared to the
preoperative statuso
129
Because of massive swelling of the
periorbi tal soft tissue of the affected side,
the upper eyelid had to be lifted by the
examiner to carry out the exophthalmometry examinations with the Hertel
exophthalmometer and optical 3D imaging in five of the patients, pre- and
postoperativelyo
Axial CT slices were used to determine
the estimated distance Aestimated• preoperatively (96 08 ± 9.1 mm, Table 3)0
The protrusion (BcT) of the sound sides
(17.4 ± 3.1 mm) and the affected sides
(18.1 ± 305 mm) was assessedo The
stattstical evaluation revealed that the
values did not differ significantly
(P = Oo249)0 The protrusion determined
from the CT images was in the same
range like the protrusion (Boptic)
assessed by the optical 3D data (sound
1706 ± 303 mm,
affected
side
side
18.4 ± 3 o7 ffiffi, p optic Sound/alleeted = 0 o07 5>
p CT/optic sound =0°812, p CT/optic aft'ected =
00239).
Hertel
exophthalmometry
showed a protrusion of 1605 ± 205 mm
on the sound side and 16.9 ± 200 mm on
the affected side. The Hertel data
showed no statistically significant difference between the two sides (P=0.427)o
They also did not differ significantly
from the corresponding data of CT and
optical 3D imaging (P CT/Hertel sound =
0°271' p optic/Hertel sound = 0°195, p CT/Hertel
afrected =00266, p optic/Hertel aftoected =0.154)0
Looking at the single measurements,
Hertel exophthalmometry revealed · a
more pronounced protrusion than the
CT data in four of five cases of a posterolaterally dislocated lateral orbital rim o
In cases without dislocation of the
lateral orbital rim, the Hertel values
showed an enophthalmos although a
posterior shift of the globe was not
apparent on the CT slices (Table 4) 0
Five days after surgery, optical 3D
imaging showed a protrusion value of
1706 ± 303 mm on the sound side that did
not differ significantly from the pre
operative value assessed with the same
technique (P=0.527)0 The affected
side revealed a protrusion value of
1708 ± 303 mm . There was no statistically
significant difference compared to the
sound side (P=0.075)o Hertel exophthalmometry showed protrusion values of
1602 ± 109 mm for the sound side and
1502 ± 2.4 mm for the affected side
revealing an enophthalmoso However,
the difference was not statistically significant for the two sides (P=Oo069)
(Tab1e 4) 0 The protrusion values determined by Hertel exophthalmometry
and optical 3D imaging also did not
differ significantly for the sound side
130
Nkenke et al.
lateral orbital margin. They can be used
for
a) absolute
exophthalmometry
to
measure exact gradations of minimal
to maximal degrees of exophthalmos
and is helpful for anthropologic
considerations,
b) relative exophthalmometry to assess
asymmetry of protrusion between the
two eyes of the same person,
c) comparative exophthalmometry to
determine a change in a person's
eye position during a given
interval 4 •7 • 17 · 20 .
Fig. 6. Facial surface assessed by optical 3D imaging (red: facial surface assessed by left CCD
camera, green: facial surface assessed by right CCD camera, black line: plane of assessment of
the facial contour).
(P=0.209), while the difference between
the two methods on the affected side was
statistically significant (P= 0.050).
Discussion
A displacement of the globe can occur
because of thyroid eye disease, intraorbital tumours and craniofacial
trauma. This shift can take place in any
direction, depending on the location of
the inciting factor. The most important
measurement done clinically is the determination of the anterior-posterior axis
with respect to the frontal plane of the
face in order to determine the relative
position of the globe within the orbital
space. Exophthalmos and enophthalmos
are understood as anterior and posterior
displacement of the eyeball, respectively.
They can be unilateral or bilateral.
Various instruments have been proposed for recording the position of the
globe. Most of them record the position
of the corneal apex in relation to the
It has been advocated that the Hertel
exophthalmometer is the most useful
instrument to evaluate protrusion.
Therefore, it has become a standard in
clinical routine and research trials.
Hertel exophthalmometry has been
criticized for its low repeatability and
low accuraci 6 •2 0 . Numerous attempts
at an improvement of devices for
exophthalmometry have been made.
Many techniques have been devised
including mechanical instruments without reliance on the lateral orbit as well as
radiographic and photogrammetric
methods11 • 15 · 2 3 •24 . None of them have
gained wide clinical acceptance because
of complexity of design, cumbersome
application and the variability of orbital
physical characteristics 14 • More than
35 different exophthalmometers have
appeared in the Iiterature attesting that,
to date, the measurement of proptosis
is not an exact science and is subject
to clinical compromise. A review of
the relevant Iiterature has been given
elsew here 14 •
Based on this knowledge, it has been
the aim of the present study to introduce
a new method of exophthalmometry,
which is based on computed tomography and easy-tc-handle, non-contact,
non-invasive, optical 3D imaging, to the
diagnostics and the follow-up of patients
suffering from zygomatic fractures with
involvement of the orbital floor and to
compare the resulting values to Hertel
exophthalmometry.
Exophthalmometers like the Hertel
device are placed on the facial surface.
The main reason for the majority of the
previous investigators of exophthalmometry to use the external orbital margin as reference point was that in this
region the soft parts are very thin making it possible to place a measuring
instrument almest directly on a sharp
skeletal edge. These methods require an
intact lateral orbital rim for fixation.
Exophthalmometry using 3D imaging
Table 20 Exophthalmometry data (patients without pathology of the orbital region)
Right
A (mrn)
BcT (mm)
Boptic (mm)
Hertel (mm)
C (mm)
D (mm)
E (mm)
BCTIA ratio
DIC ratio
BcT-E/2 (mm)
Boptic-EI2 (mm)
Hertei-EI2 (mrn)
p
Left
9606 ± 705
1607 ± 405
1606 ± 4.4
1602 ± 408
3509 ± 305
1202 ± 309
2402 ± 200
0017 ± 0004
0034 ± 0009
406 ± 400
405 ± 309
401 ±406
There are many orbital conditions in
which the orbital rim is altered and the
instruments cannot be used reliablyo The
results of the measurements are affected
by asymmetries and other variations in
the facial skeletono It is easy to understand that the wide individual variations
in the facial skeleton are probably the
main cause of the great difference in
values obtained already for a normal
populationo With regard to these factors,
there is a clear limit to dassie exophthalmometry already in measuring normal values of protrusion in healthy
subjects 4 •7
With
Hertel
exophthalmometry,
errors in measurement can commonly
occur, when the footplate is incorrectly
positioned on the lateral orbital rimo
Since these exophthalmometers are
placed on soft tissue, the position of the
reference point is dependent on the
investigator. In order to reduce this
practical error, it has been recommended
that the same examiner performs the
measurements to prevent interpersonal
difference in estimating the same patient.
However, it seems that error is inevitable
and results in a large difference in protrusiono Another factor that influences
the result of exophthalmometry is that
although the footplate maybe placed
accurately, the protrusion value may be
different according to the state of the
tissue and the degree of compressiono In
normal cases, the thickness of the soft
tissue varies rather insignificantly4 This
is reflected by the results of the present
study, where the values of absolute
exophthalmometry assessed by the
Hertel device for the normal population
0
0
1607 ±
1606 ±
1606 ±
3600 ±
12.4 ±
2402 ±
0017 ±
Oo34 ±
406 ±
405 ±
405 ±
4.4
4.4
307
3.4
400
200
0004
0009
309
309
306
I
00655
00689
00525
00180
00305
1.0
00655
00374
00892
00892
00525
did not show relevant differences compared to the computed tomography
measurements oThey werein the range of
previous studies 13 In connection with
certain conditions of disease, such as a
displacement of the lateral orbital rim or
soft tissue oedema caused by an injury or
being related to an Operation, extensive
changes can be found implying a source
of error 8 •22 In the present study, periorbital oedema led to an underestimation of the degree of protrusion of the
injured sides, while a posterior displacement of the lateral orbital rim caused an
overestimation of the protrusion, when
the data were compared to computed
tomography
Contrary to Hertel exophthalmometry, the assessment of data by computed
tomography and 3D imagihg is irrespective of the examiner. CT has been recommended for preoperative evaluation
of orbital trauma as a standard diagnostic technique 6 Baseline exophthalmometry data can be extracted from these
images providing the bony lateral orbital
rim as landmark 9 . During the follow-up,
the superimposition of CT and optical
data provide a good visualization of the
changes of the globe position after surgery. The use of two-dimensional contours of the globe for relative and
comparative exophthalmometry has
been proposed many years before 1 •
Because of their two-dimensional
nature, axial CT slices and optical contours can be easily merged to a single
data set with little deviation as the data
of the healthy orbits and the preoperative data of the zygomatic fractures have
shown in the present study.
0
0
0
0
Table 3. Exophthalmometry data (patients suffering from zygomatic fractures)
Sound side
Acstimated (mm)
C (mm)
D (mm)
E (mm)
Affected side
p
3709 ± 201
1408 ± 207
24.4 ± 1.9
I
00109
00141
00109
9608 ± 9.1
37 07 ± 202
1306 ± 2.9
2402 ± 1.9
131
The assessment of data by Hertel
exophthalmometry uses only one dimension and does not provide any visualizationo Therefore, data superimposition
with computed tomography is per se
impossible.
For Hertel exophthalmometry and
optical 3D imaging without computed
tomography data as reference, it is
impossible to decide whether a difference
in the sagittal projection of the corneal
apex is the consequence of a change in
size of the globe based on enlargement
or shrinking is caused by a proptosiso
To make sure that the axial length
of the globe has remained unchanged,
radiological examinations by orbital
computed tomography have to be performed in order to receive reliable
measuremen ts
In orbital trauma with dislocation of
the globe, an ideal pre-event calibration
is not available, but an estimation can be
given by computed tomography using
the intact opposite orbit as baseline in
unilateral cases as it has been done in
the present studyo These estimated data
provide information about the globe
position status within the orbit of the
affected side for planning the surgical
strategy 19
Computed tomography is accepted as
tool for primary diagnostics of orbital
trauma. It exposes the patient to
irradiation. The use for postoperative
follow-up examinations has to be confined to cases, where information on
intraorbital structures is neededo If only
the determination of the globe position
is intended during the follow-up examinations, the application of non-ionizing
optical 3D imaging is adequateo
In orbital trauma, the difference in
proptosis between the two sides is more
important than the absolute exophthalmometry valueso To decide, whether a
difference is pathological or not, the
normal ranges of proptosis have to be
knowno A proptosis below 2 mm is not
considered a relevant exophthalmos 3 •20
In the present study, the data of two
patients with zygomatic fractures
revealed a difference of more than 2 mm
using Hertel exophthalmometry (Table
4, patients 11 and 12)0 CT images clearly
showed a less pronounced differenceo It
is obvious that in these cases the use of
Hertel exophthalmometry alone might
have led to wrong conclusions.
Graves orbitopathy is another field, in
which optical 3D imaging for exophthalmometry purposes will be of benefit for
future patients 2 1 • The intraoperative
application of this technique allows to
0
0
0
...I.
(,.)
1\)
~
rr~
~
~
:--
Table 4. Exophthalmometry data (patients suffering from zygomatic fractures)
Patient
l
2
3
4
5
6
7
8
9
10
11
12
Mean± SO
p
Dislocation
of the lateral
orbital rim
BcTpreop
Sound side
(mm)
BcTpreop
Affected side
(mm)
Boptic preop
Sound side
(mm)
Bopticpreop
Affected side
(mm)
Hertelpreop
Sound side
(mm)
Hertelpreop
Affected side
(mm)
Boptic postop
Sound side
(mm)
Boptic postop
Affected side
(mm)
Hertelpostop
Sound side
(mm)
Hertelpostop
Affected side
(mm)
No
No
Yes
Yes
No
No
No
Yes
No
No
Yes
Yes
22.8
18.0
16.0
14.1
18.0
20.7
20.7
17.3
18.5
16.0
15.4
11.6
17.4±3.1
22.8
22.0
16.0
16.5
21.3
20.0
21.4
17.3
18.5
16.0
13.9
11.6
18.1 ± 3.5
22.6
18.3
16.0
13.8
18.1
22.6
20.9
17.3
18.2
15.8
15.4
11.9
17.6 ± 3.3
22.7
21.7
16.0
16.6
21.5
22.7
21.6
17.4
18.7
16.0
13.8
11.5
18.4 ± 3.7
18
17
13
16
17
18
17
14
22
17
16
13
16.5 ± 2.5
17
16
14
17
16
17
17
16
22
16
19
16
16.9 ± 2.0
22.6
18.3
16.0
14.0
18.2
22.6
20.7
17.3
18.2
16.3
15.5
11.7
17.6 ± 3.3
22.8
18.7
16.0
14.4
18.6
22.8
20.9
17.5
18.4
16.4
15.6
11.9
17.8 ± 3.3
16
17
13
16
17
16
17
12
18
17
19
16
16.2 ± 1.9
15
14
12
16
14
15
15
13
21
16
18
13
15.2±2.4
I
I
0.249
0.075
0.427
0.075
0.069
Exophthalmometry using 3D imaging
replace the Hertel measurements for the
control of the correction of exophthalmos. During the follow-up postoperative
CT scans can be avoided by the use of
optical 3D imaging in cases where the
main interest is focused on exophthalmometry.
Further software improvements will
permit the superimposition of 3D data
sets of computed tomography and optical sensors to allow for a threedimensional evaluation of the change of
globe position without loss of information. In the future, it will be possible to
assess the volume change of the orbit
by means of the initial CT and the
optical follow-up examinations without
additional exposure of the patient to
irradiation.
Although optical 3D imaging requires
a complex measuring device and the use
of contact lenses, it is a relevant method
for the improvement of relative and
comparative exophthalmometry. The
clinical applications of optical 3D imaging are not limited to the assessment of
globe position but are multifaceted.
They range from simple documentation
of the facial surface to the intraoperative
assessment of the changes in facial
contour 12 • 18 .
The Hertel exophthalmometer will
continue to serve as standard in clinical
measurement of the globe position. The
combination of computed tomography
and 3D imaging technique will have
its applications especially in complex
reconstructions.
Acknowledgments. The study was supported by the 'Deutsche Forschungsgemeinschaft' (Special Research Sector
603, Model-Based Analysis and Visualization of Complex Scenes and Sensor
Data-Subproject C4).
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Address:
Dr Dr Emeka Nkenke
Department of Oral and Max illofacial
Surgery
University of Erlangen-Nuremberg
Glueckstr. 11
91054 Erlangen
Germany
Tel: + +49-9131-8533653
Fax: + +49-9131-8534219
E-mail:
emeka. nkenke@mkg. imed. uni-erlangen. de